Concrete reinforcing bars with deep alveoli



April 23, 1968 A BUGAN I 3,378,985

CONCRETE REINFORCING BARS WITH DEEP ALVEOLI Filed Nov. 27, 1965INVENTOR.

ANTON QUGAIV A TTOQNEY United States Patent ()fi 3,378,985 Patented Apr.23, 1968 ice 3,378,985 CQNCRETE REINFORCING BARS WITH DEEP ALVEOLI AntonBugan, Via Rodriquez Pereira 206, Rome, Italy Filed Nov. 27, 1963, Ser.No. 326,445 Claims priority, application Austria, Nov. 29, 1962, A9,379/62 5 Claims. (Cl. 52-739) This invention relates to a concretereinforcing bar of hexagonal cross-section.

In building, and particularly in engineering structures, there areincreasing requirements for heavy structures of reinforced concretewhich are widely spanned and/or heavily loaded. The erection of suchstructures makes necessary the use of reinforcement of great bearingcapacity capable of supporting high tensile or compression stressesguaranteeing full safety also in thick bars.

Of course, reinforcements from thick smooth round bars stressed at hightensions would lead to excessive cracks on beams or tie rods. Suchcracks facilitate the access of humidity, water and/or other damagingelements to the reinforcements, thus causing their rusting and inextreme cases, the collapse of the whole structure. Therefore, therecent regulations of advanced countries limit the crack widths at 0.1mm. up to 0.3 mm., depending on the function of the structures involved.

Since the crack width represents the decisive criterion for the safetyof reinforced concrete structures, prominent experts carried outextensive systematic research in order to develop formulas fordetermining the crack width. This diminishes, when the bond betweenreinforcing bars and concrete increases. In this respect, several shapeswere given to reinforcing bars, nevertheless, they do not satisfy themain requirement of the theory of reinforced concrete for a perfectunity of the bars with the concrete.

Thus, a reinforcing bar having the cross-section of a six-pointed starwith transverse ribs, the flanks of which decline at 30 from the sidesof the circumscribed hexagon, is known as one of the best. However,during industrial production, this angle was reduced by wearing of thechannels and the deepness of the alveoli became insuflicient toguarantee the required bond strength. Therefore, it was necessary tochange the channels often and to interrupt the rolling two or threetimes during a shift. These costly channels with many transverseincisions were often elaborated upon, thus the consumption on rollerswas excessive. Moreover, the transverse ribs reduce the strength of suchbars under many repeated loads of bridges and similar structures.

The present invention is directed to a concrete reinforcing bar of across-section and of such surface shapes which guarantees theabove-mentioned perfect unity with concrete, thus reducing the crackwidths on the allowable measures, which facilitates manufacturing andregular bending of the bar.

The bar consists essentially of four pair of flanks which aresymmetrical to one of the longest symmetrical axes SS and decline fromthe sides of the circumscribing hexagon at more than 30, and from theremaining two pair of symmetrical flanks which are nearly perpendicularto the axis SS declining from the sides of hexagon at nearly 30. As aresult, this bar has six basic deep grooves which are divided in deep,narrow and short alveoli by closely spaced transverse or diagonal ribs,flat with the side of the circumscribing hexagon.

The angles over 30 between the flanks and the hexagon sides permitturning the grooves on rollers with two tools having one cutting edge orby means of a single tool with two edges without damaging the adjacentlongitudinal ribs of the channel.

The diagonal ribs are advantageous for structures which are susceptibleof repeated dynamical loadings. The transverse forces caused by theinclination of the diagonal ribs are absorbed by the neighboringlongitudinal ribs. Thus, there will be eliminated the splitting ofconcrete existing when pulling of other types of bars with extendingtransverse ribs and particularly diagonal ribs.

It is also possible to mark one quality steel by means of transverseribs, another quality steel by means of ribs inclined to the left and athird quality steel by means of ribs inclined to the right as shown inFIGURE 3 of the drawings. Such a clear marking is of great practicalimportance for the safety of structures, as it eliminates any mistakesof the steel quality in mills, on stocks, on plots, as well as instructures, even after a long period of installation. The flattransverse or diagonal ribs of these bars when bent, eliminate theconcentrated pressures on them from the pin which presses uniformly ontheir longitudinal ribs. Thus, fragility is also eliminated. Also, thepulling of the bars from stocks and the bending thereof is facilitated.

The bar according to this application can also be shaped in a differentmanner.

When the bar is thick, the alveoli would become too wide and thetransverse ribs too thick; thus, the gripping of the concrete in thedepth of the ribs will be insuflicient, and there would be an increasein the consumption of steel for transverse ribs which do not collaboratein longitudinal stresses. Therefore, it is very advantageous to insertone or more secondary longitudinal basic ribs into such widelongitudinal grooves; their external edges lie on sides of thecircumscribing hexagon and their flanks are parallel to those of theclosely disposed longitudinal main ribs.

The manufacturing of all of these bars is easy. Moreover, thesymmetrical and regular distribution of material in each cross-sectionfacilitates the bending of the bars, all of which is of great practicalimportance.

Preferred embodiments of bars made in accordance with this invention areshown in the attached drawings in which:

FIGURE 1 shows a bar, the cross section of which is a six point starwith steep flanks, the longitudinal grooves being interrupted bydiagonal ribs r inclined to left as viewed in the drawing.

FIGURE 2 shows a thick reinforcing bar of the basic cross sectionaccordin to the FIGURE 1, but with two secondary longitudinal ribs ineach of the six basic grooves having edges on the sides of thecircumscribing hexagon. The longitudinal grooves are interrupted bytransverse ribs 1'.

FIGURE 3 shows a bar, the cross section of which consists of two halvesof the cross section according to the FIGURE 1 (turned at among whichthree pairs of trapezoids are inserted having their edges on the side ofthe circumscribing prolonged hexagon. The grooves are interrupted byribs r, inclined to the right as viewed in the drawing.

In all of these figures the imaginary sides of circumscribing hexagonare identified as p, the flanks which decline from the side 1) more thanat 30 as f, and the flanks which decline from the side 1) less than at30 as f.

I claim:

1. A longitudinally grooved concrete reinforcing bar of six-pointed starshape in cross section including two pairs of flanks symmetrical to oneof the longest symmetrical axes SS declining from the sides of thecircumscribing hexagon at nearly 30, characterized by four pairs of mainflanks symmetrical to said symmetrical axis and declining at an anglegreater than 30 from the sides of the hexagon, and a plurality ofdiagonal ribs rolled in the longitudinal grooves of the bar.

2. The reinforcing bar according to claim 1, characterized by onesecondary longitudinal rib located in the basic grooves of the bar,where as the edges of these ribs lie on sides of the circumscribinghexagon and their flanks have the same declination from the hexagonsides as the corresponding flanks of the basic grooves.

3. The reinforcing bar according to claim 1, characterized by aplurality of secondary longitudinal ribs located in the basic grooves ofthe bar, whereas the edges of these ribs lie on sides of thecircumscribing hexagon and their flanks have the same declination fromthe hexagon sides as the corresponding flanks of the basic grooves.

4. The bar according to claim 1, characterized by one pair of adjacenttrapezoids formed perpendicularly to the longer symmetrical axis SSbetween the two halves of the basic cross section, Whereas the edges ofthe trapezoids lie on the sides of the circumscribing hexagon and theflanks decline from the latter at the same degree as the correspondingflanks of the basic grooves.

5. The bar according to claim 1, characterized by a plurality of pairsof adjacent trapezoids formed perpendicularly to the longer symmetricalaxis S-S between the two halves of the basic cross section, whereas theedges of the trapezoids lie on the sides of the circumscribing hexagonand the flanks decline from the latter at the same degree as thecorresponding flanks of the basic grooves.

References Cited UNITED STATES PATENTS 2,246,578 6/1941 Salardi 52737FOREIGN PATENTS 229,426 7/ 1960 Australia. 610,712 12/1960 Canada.1,189,956 3/1959 France.

FRANK L. ABBOTT, Primary Examiner.

JAMES L. RIDGILL, Examiner.

1. A LONGITUDINALLY GROOVED CONCRETE REINFORCING BAR OF SIX-POINTED STARSHAPE IN CROSS SECTION INCLUDING TWO PAIRS OF FLANKS SYMMETRICAL TO ONEOF THE LONGEST SYMMETRICAL AXES S-S DECLINING FROM THE SIDES OF THECIRCUMSCRIBING HEXAGON AT NEARLY 30*, CHARACTERIZED BY FOUR PAIRS OFMAIN FLANKS SYMMETRICAL TO SAID SYMMETRICAL AXIS AND DECLINING AT ANANGLE GREATER THAN 30* FROM THE SIDES OF THE HEXAGON, AND A PLURALITY OFDIAGONAL RIBS ROLLED IN THE LONGITUDINAL GROOVES OF THE BAR.